Tag: plant tissues

Sclerenchyma is the simple permanent tissue present in plants that performs the function of protection and support. Two types of sclerenchyma cells exist, fibers and sclereids. Fibres are long, narrow-lumen, thick-walled and dead cells that provide support to the internal structure of plants. Sclereids are polygonal cells that are found in fruit pulp. Parenchyma has think walled, polygonal and live cells while collenchyma has angular thickened polygonal cells.

The exocarp is the thin outermost layer (or skin) of the fruit. The mesocarp is a thick husk composed of coarse brown fibers (coir). The endocarp is the hard, but relatively thin woody inner layer of a fruit that contains the endosperm. The endosperm is partly liquid (“coconut water”) and partly solid (fibrous white coconut “flesh” or “meat”, which adheres to the inner wall of the endocarp).

There are four types of tissues present in the plants, namely vascular tissue, epidermal tissue, ground tissue and meristematic tissue. Ground tissue consists of parenchyma tissue, collenchyma tissue and sclerenchyma tissue. Parenchyma cells have thin primary walls and remain alive after they become mature. Collenchyma cells have thin primary walls with secondary thickening in some areas. They provide mechanical and structural support.

Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants. The presence of numerous sclereids form the cores of apples and produce the gritty texture of guavas and pears.

Sclerenchyma, in plants, support tissue composed of any of various kinds of hard woody cells. Mature sclerenchyma cells are usually dead cells that have heavily thickened secondary walls containing lignin. 

1. A tissue whose cells have very thick cell wall are sclerenchyma. 
2. The cells wall is rigid and lignified.
   

Since plants do not have bones for structure and support they must have cell walls around all of their cells. This leads to the need for very unique cells in plants. Sclerenchyma cells are specialized plant cells that exist to provide strength and support. They are present in all kinds of plants including grasses, trees, and flowering plants.

Protoxylem and protophloem that develop in the primary stage of plants need living cells to divide and form more tissues to grow and as sclerenchymatous cells are dead and not divide so they lack sclerenchyma cells.

• Permanent tissues may be defined as a group of living or dead cells formed by meristematic tissue and have lost their ability to divide and have permanently placed at fixed positions in the plant body. Meristematic tissues that take up a specific role lose the ability to divide. This process of taking up a permanent shape, size and a function is called cellular differentiation. Cells of meristematic tissue differentiate to form different types of permanent tissues.
  

Pits are thin portions of the cell wall. Through pits, the communication and exchange of fluid takes place between cells.  There is no deposition of lignin in this area. They are found in the walls of dead tissues with lignified cell walls like sclerenchyma and tracheids and vessels of xylem.